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SubjectRe: [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()
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On 1/9/20 12:40 PM, Peter Ujfalusi wrote:
>
>
> On 09/01/2020 13.29, Fabrice Gasnier wrote:
>> On 1/9/20 11:32 AM, Peter Ujfalusi wrote:
>>>
>>>
>>> On 09/01/2020 11.13, Fabrice Gasnier wrote:
>>>> On 1/7/20 12:45 PM, Peter Ujfalusi wrote:
>>>>> dma_request_slave_channel() is a wrapper on top of dma_request_chan()
>>>>> eating up the error code.
>>>>>
>>>>> By using dma_request_chan() directly the driver can support deferred
>>>>> probing against DMA.
>>>>>
>>>>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
>>>>> ---
>>>>> Hi,
>>>>>
>>>>> Changes since v1:
>>>>> - Fall back to IRQ mode for ADC only in case of ENODEV
>>>>
>>>> Hi Peter,
>>>>
>>>> Thanks for the patch,
>>>>
>>>> Please find a minor comment here after. Apart from that, you can add my:
>>>>
>>>> Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
>>>>
>>>>
>>>>>
>>>>> Regards,
>>>>> Peter
>>>>>
>>>>> drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
>>>>> 1 file changed, 17 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
>>>>> index e493242c266e..74a2211bdff4 100644
>>>>> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
>>>>> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
>>>>> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
>>>>> {
>>>>> struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
>>>>>
>>>>> - adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
>>>>> - if (!adc->dma_chan)
>>>>> - return -EINVAL;
>>>>> + adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
>>>>> + if (IS_ERR(adc->dma_chan)) {
>>>>> + int ret = PTR_ERR(adc->dma_chan);
>>>>> +
>>>>> + adc->dma_chan = NULL;
>>>>> + return ret;
>>>>
>>>> You may "return PTR_ERR(adc->dma_chan);" directly here.
>>>
>>> I don't make decision here on behalf of the adc path on to go forward w/
>>> or w/o DMA support and if we go ahead the stm32_dfsdm_dma_release()
>>> needs the dma_chan to be NULL in case we don't use DMA.
>>>
>>> It is much cleaner to set dma_chan to NULL here than doing it in other
>>> paths.
>>
>> Hi Peter,
>
> Hi Fabrice,
>
>> Sorry I wasn't clear enough. I agree with you. I was suggesting only,
>> talking about the 'ret' variable. It may be removed to spare a few lines
>> :-).
>> if (IS_ERR(adc->dma_chan)) {
>> adc->dma_chan = NULL;
>> return PTR_ERR(adc->dma_chan);
>> }
>> I'm okay both ways.
>
> PTR_ERR(NULL); will return 0
> I need to retrieve the actual error code before NULLing dma_chan.

Oh yes, so please forget this.
Thanks,
Fabrice

>
>>
>>>
>>>>
>>>> Best Regards,
>>>> Fabrice
>>>>
>>>>> + }
>>>>>
>>>>> adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
>>>>> DFSDM_DMA_BUFFER_SIZE,
>>>>> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
>>>>> init_completion(&adc->completion);
>>>>>
>>>>> /* Optionally request DMA */
>>>>> - if (stm32_dfsdm_dma_request(indio_dev)) {
>>>>> + ret = stm32_dfsdm_dma_request(indio_dev);
>>>>> + if (ret) {
>>>>> + if (ret != -ENODEV) {
>>>>> + if (ret != -EPROBE_DEFER)
>>>>> + dev_err(&indio_dev->dev,
>>>>> + "DMA channel request failed with %d\n",
>>>>> + ret);
>>>>> + return ret;
>>>>> + }
>>>>> +
>>>>> dev_dbg(&indio_dev->dev, "No DMA support\n");
>>>>> return 0;
>>>>> }
>>>>>
>>>
>>> - Péter
>>>
>>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>>
>
> - Péter
>
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>

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